System architecture evolution (SAE) is an upgrade plan of the 3GPP for a core network architecture of an LTE wireless communications standard. An SAE architecture is shown in FIG. 1. For the SAE architecture, if a UE moves across TAs, the UE triggers a tracking area update (TAU). When neither an MME nor an S-GW changes, in a process of executing a TAU procedure, there is not any signaling interaction between the MME and the S-GW. A TA (Tracking Area) is a geographical area formed by continuously covered cells, and is used to manage a location of a UE that is in an idle state.
In the SAE architecture, a gateway still needs to keep a large quantity of external signaling interfaces. The large quantity of external signaling interfaces of the gateway bring a large amount of interface signaling. A gateway that uses a dedicated hardware platform does not have strong signaling processing performance, and therefore, easily becomes a bottleneck. Software-defined networking (SDN) provides an effective way to resolve the bottleneck problem of the gateway in signaling processing. An SDN-based SAE architecture is shown in FIG. 2.
With the rapid development of a mobile Internet and the popularity of intelligent terminals, mobile traffic presents a trend of an explosive growth. In order to avoid pressure that a growth in mobile traffic brings to a core network, a mobile gateway presents a trend of gradual downward deployment and distributed deployment. For the SDN-based SAE architecture shown in FIG. 2, GW-Us are further moved downwards and deployed in a distributed manner, implementing an architecture of distributed GW-U deployment shown in FIG. 3.
However, in a distributed gateway architecture, in a process of executing a TAU procedure, it may be necessary to select a new GW-U and establish a new PDN (packet data network) connection for a UE. Because an MME cannot obtain information about GW-U deployment, GW-U updating cannot be implemented when neither the MME nor a GW-C changes.